Outside the building on the first day of the public hearing of the royal commission into institutional responses to child sexual abuse, representatives from the Care Leavers Australia Network (Clan), an advocacy and support group for people who grew up in Australian institutions and suffered abuse, gathered in the wind and rain to make their presence felt.

Inside, the commission would hear from two men who were assaulted as children by their former scout leader, the since-convicted paedophile Steven Larkins. It also heard from former scout leaders and employees who faced the hearing to answer questions as to how a man who was the subject of police investigations and numerous allegations of suspicious behaviour was allowed to remain working with children for years.

In his opening address, Justice Peter McClellan said: "I did not adequately appreciate the devastation and long-lasting effect which sexual abuse, however inflicted, can have on an individual's life.

"It is reported to us that when it occurs in residential institutions, sexual abuse is almost always accompanied by almost unbelievable levels of physical violence.

"Many of the stories we are hearing will shock people."

Clan member Yvette Parr and her two sisters spent about two years in the 1950s in the Convent of the Good Shepherd in Melbourne, where Parr said they faced abuse and neglect after being abandoned by their father.

"We were subjected to some, I don't even know how to explain it," said Parr, trailing off.

"My little sister started wetting the bed again and the nuns made her wear the knickers on her head and wet sheets around her shoulders and paraded her around and called her 'smelly'. Awful stuff.

"[My sisters] don't want to be here but they don't stop me – they support me because I'm here for them, too."

Parr – who said she was also sexually abused as a child – has never had counselling and doesn't know what she wants to hear at the commission.

Sunday was a sleepless night for her. She said she didn't know that Larkins had gone on to work at Kendall Grange, a school for troubled boys where more than a dozen former students allege they were abused by a St John of God brother during the 1970s and 1980s.

"I'm here to support these kids and the people that have got the courage to be here today," she said. "Just so they know that they are loved. Because we're family to them.

"I'm here to tell my story because I back up what happened to the other kids."

Clan executive officer Leonie Sheedy said the group had been calling for this royal commission since Clan was established in 2000, when 300 people attended its first meeting in Ashfield. Sheedy said they were naive to have held the meeting in a church – many people were too traumatised to enter a building that represented the abuse they suffered as children.

For close to 15 years Clan has lobbied for the royal commission, a Senate inquiry and a compensation scheme. Members sent 10,000 postcards to former prime minister Julia Gillard, who announced the commission in 2012.

"There are 500,000 Australians who were raised in the 800 or more orphanages and children's homes, and we're invisible.

"We haven't spoken about our trauma and abuse and neglect because as children we were told that we were no-hopers in life, that we were going to end up as prostitutes and in jail. It takes us half our lifetime to find our voice, if we do at all."

Sheedy and her fellow Clan members hope that their presence encourages more people to come forward with their story and shift the burden of shame "squarely on the government, the churches and the charities who failed in their duty of care to you as a child".

"Don't take this story to the grave, because your story won't do anybody any good in the coffin," she said.